Vacuum-pump



M. LEITCH.

VACUUM PUMP.

APPLICATION FILED FEB. s. 1920.

Patented Feb. 8, 1921.

2 SHEETSSHEET I- M. LEITCH.

VACUUM PUMP.

APPLICATION FILED FEB. 3. 1920.

1,367,554, Patented Feb. 8, 1921.

2 SHEETS-SHEET 2.

ArfM/VEX UNITED STATES PATENT OFFICE.

MEREDITH LEI'ICH, OF POUGHKEEPSIE, NEW YORK, ASSIGNOR TO THE DE LAVA]; SEPARATOR COMPANY, OF NEW YORK, N. Y-, A. CORPORATION 01' NEW JERSEY.

VACUUM-PUMP.

Specification of Letters Patent.

Patented Feb. 8, 1921.

Application filed February 3, 1920. Serial No. 356,014.

To all whom itmay concern:

Be it known that I, MEREDITH Lnrron, a citizen of the United States, residing at loughkee sie, county of Dutchess, and State of New ork, have invented a new anduseful Improvement in Vacuum-Pumps, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, which form a part of this specification.

My invention relates to vacuum pumps of the known ty e having an approximately cylindrical b0 y in which there is eccentrically mounted a rotor having vanes adapted to slide out against the inside of the body.

In pumps of this type it is necessary, in order to have the pump run easily, to have appreciable clearances between parts. This causes excessive leakage. Such leakage has been overcome by sealing the pump with a liquid, usually oil.

It is known, in a pressure pump, to-provide an oil separator on the discharge pipe and a passage for forced return of the separated oil to the inside of the rotor, which is thus kept full of oil at a pressure equal to the discharge pressure. Part of this oil is forced out through the bearings, thus lubrieating them, the oil finally draining back to the inlet side of the pump, which is at atmospheric pressure. Because the oil in the rotor is at a pressure higher than atmospheric, it is necessary that the ends of the rotor be tightly closed by the pump heads and it is impossible to gravitationally return to the system drips from bearings, etc. l/Vith a vacuum pump provided with a similar lubricating arrangement, any opening for a return of oil to the inlet side of the pump would admit air and seriously interfere with the production of a vacuum.

In my improved pump I utilize this known oil circulation system to the extent of using oil to seal clearances in the pump and a separator to remove oil from the air discharged by the pump. In order that I may easily return to the system oil from the ends of the bearings, I maintain atmospheric pressure inside the rotor by openings through the pump heads to the atmosphere. To supply oil for sealing I provide reservoirs in the pump heads. In order to catch oil drips from bearings, the highest oil level is arranged below the bottom of the pulley hub.

In order to maintain the oil seal, the lowest ()11 level is arranged at a distance below the center of rotation not greater than the inside radius of the annulus of oil required for sealmg. In order to have a sufiicient storage capacity with a small change in level, the oil reservoirs are of large horizontal dimensions.

Innormal operation, my improved pump is designed to exhaust air from a pipe system at about one-half of atmospheric pressure and to discharge it at atmospheric pressure. Each time that the pump is started it at first takes air at atmospheric pressure and, before the discharge port opens, com presses it to double that pressure. This causes a leak past the ends of the rotor, which tends to raise the pressure therein and blow the oil out of it. This rise of pressure s prevented, in my construction, by providmg large openmgs from the interiorof the rotor through the heads of the pump into the oil reservoirs and liberal air outlet-s from the oil reservoirs.

I know that it is old to seal the rotor of a pump with a body of oil. I know that it is old to use, on the discharge pipe of a pump, a separator to take the oil out of the discharged air. I know that it is old to return this oil under pressure to the inside of a rotor having its ends covered by the pump heads so as to retain the oil. I know that it is old to convey oil drips from bean ings to the suction side of a pump so as to return them to the inside of the pump. These features, therefore, are not herein claimed as my invention.

The main features of novelty in my in vention are: the sealing, with an annulus of oil, of a rotor having free communication with the atmosphere, the provision of oil reservoirs which are in free communication with the atmosphere and which, when the pump stops, will receive all oil discharged from the annulus and when the pump starts will return oil to reform the annulus inside of the rotor, and the gravitational return of all bearing drips to the sealing body of oil.

In the accompanying drawings, which illustrate a preferred embodiment of my invention:-

Figure 1 is a section through the pump parallel to the center line of the shaft,

a crank pin 16. This crank pin Fig. 2. is a section at right angles to the center line of the shaft on the line 22 of Fig. 1.

Fig. 3 is a section through one of the oil reservoirs on the line 3-3 of Fig. 1.

The rotor a is mounted on a shaft 6 carried by hearings in the heads 0 and d. The rotor has four slots in which wings or vanes c slide toward and from the shaft. Spacers f maintain a uniform distance between opposite vanes. In the outer edges of the vanes e are grooves in which semi-circular rods 9 oscillate.

Between the heads a and ais a housing h having a bore of such shape that all diameters (or chords) measured throughthe center of the shaft 6 are equal. At one side of the housing is an inlet chamber 71 connected with the bore by the ports 7' and at the other side is an outlet chamber is connected with the bore by the port Z. From the outlet chamber 1: a passage m leads to the central chamber of the oil separator, the upper half of which is separated from the side chambers by the half partitions n and 0. From the side chambers, passages 12 lead to the exhaust pipe. Across the bottom of the central chamber is a dividing fence q. From the side chamber of the oil separator there lead to the shaft, oil holes rand shaving branches 2? and u communicating with the inside of the rotor a.

Formed within the heads 0 and d are oil reservoirs o and 'w communicating with the inside of the rotor a by holes at and y having their lower edges above the bottom of the in side of the rotor. One head (Z carries a hollow axle 10 around which the pulley 11 revolves on bearing rollers 12 and drives the shaft 6 through the flexible coupling 13.

One end of the shaft Z) carries a pinion 14: meshing with and driving a gear 15 carrying drives a block 17 in a slotted pendulum 18 oscillating about an adjustable fulcrum 19 and operating a reciprocating valve 20 on the valve seat 21. The valve 20 is intended for use as a master pulsator valve for milking machines.

In order to have an easy running pump the rotor a is made slightly shorter than the housing k, giving clearance between it and the heads, and it is so located that there is an appreciable clearance between the top of the rotor and the top of the housing. The vanes e are made easy fits in their slots and the separators f are made so short that the vanes turn freely in the housing. These clearances, while desirable for easy running, all tend to cause leakage.

' When in operation, the pump should contain sufficient oil to cause the level in the reservoirs 'v and w to reach about onequarter inch to three-eighth inch above the bottom of the holes a; and y. This oil will flow through the holes until it fills the annular space from the bottom of the holes outward to the shell of the rotor. Centrifugal force, due to the rapid rotation of this oil, will prevent the entrance of excess oil. Centrifugal force will also force the oil into all the clearance spaces and so seal them. Oil that passes outward between the rotor and the heads and through the clearances at the sides of the vanes will seal the ends and outer edges of the vanes. Any excess oil reaching the spaces between the rotor and the housing will be thrown, with the discharging air, outward through the ports 1 into the chamber is and then upward at high velocity'through the passage m. Because of the circular path that the air is compelled to take in the oil separator, all oil in appreciable sized drops will be thrown against the wall and will collect in the bottom, while the air will pass under the partitions 'n and 0, upward through the passages p, and out through the exhaust pipe. As the oil flows down the back wall of the separator, it will be divided, by the fence 9, into two streams, one flowing to each end of the separator and thence downward through the holes 1' and s to lubricate the bearings. All oil in excess of that required for the bearings will flow through the holes 13 and u to the interior of the rotor, ready to repeat the cycle.

Oil that works outward through the bearing in the head 0 falls into the reservoir o. Oil that works outward through the bearing in the head d enters the hub of the pulley l1 and oils the roller bearing. When the hub is filled with oil, any additlonal supply forces some out through the hole 22 in the inner flange of the hub, whence it escapes into the reservoir 10.

When the pump stops, all the oil from the annulus inside the rotor, with all oil from the separator, falls to the bottom of the rotor and a large part of it flows outward through the holes m and y, to be stored in the reservoirs v and 40 until needed again.

If the pump stands idle for a long time, much of the oil from the reservoirs 'v and 'u) may leak past the rotor into the bottom of the housing. When the pump is started, the first turn will throw this oil up into the separator, whence it will flow, partly by the holes 1" and t and partly by the holes 8 and u,

to the inside of the rotor, ready to perform its sealing and lubricating function.

With the described construction of separator, oil holes, and oil reservoirs, all working parts of the pump are copiously lubricated. All clearances desirable for easy running are sealed with oil received from reservoirs open to the atmosphere and at a lower level than any drips.

It has been found practically impossible to injure one of these pumps by running dry, for before the oil level is so low as to fail of lubricating, it will fail to seal and the pump will leak so badly as to be ineffective.

The ports j and Z are-so located and proportioned as to obtain a maximum capacity and also to reduce to a minimum the atomization of oil at the discharge and thus pre vent the air flowing out through the oil separator carrying with it any substantial amount of finely divided oil. This feature of the construction herein shown is not, however, my invention, but forms the subject-matter of another application filed by Selden H. Hall February 3, 1920, Serial No. 355,999.

Nor do 1 herein claim the gear and pendulum operated valve herein shown and briefly described, as these are claimed and more fully described in a separate application filed by me February 26, 1920, Serial N 0. 361,609.

Having now fully described my invention, what I claim and desire to protect by Letters Patent is:

1. In a vacuum pump of the sliding vane type, the combination with a body, a rotor,

-vanes having appreciable clearances, a rotor shaft, bearings and driving pulley, of oil reservoirs open to the atmosphere adapted to catch drips from the bearings and the pulle hub and to maintain a sealing body of oi within the rotor.

2. In a vacuum pump of the sliding vane type, the combination with a body, a rotor and vanes having appreciable clearances, of oil reservoirs below the bearings open to the atmosphere adapted, when the pump starts, to supply oil to form a sealing annulus within the rotor and when the pump stops to receive said oil without overflow.

3. In a vacuum pump of the slidingvane type, the combination with a body, a rotor,

vanes having appreciable clearances, a shaft for the rotor, bearings therefor, an oil separator on the exhaust passage from the pump, there being an oil passage from the oil separator to each bearing and a branch passage from each of the above passages to the interior of the rotor, of oil reservoirs below the bearings, freely open to the atmosphere, adapted to receive all drips from thebearings, to supply oil to the rotor to form a sealing annulus therein during the time of its rotation and to receive all said oil without overflow at the time of its stoppage.

4. In a rotary vacuum pump, the combination with a housing having a central bore, an inlet chamber and ports therefrom to the central bore, an outlet chamber and a port from the central bore thereto, a shaft, a hollow rotor thereon eccentric to the housing, sliding vanes adapted to extend from the rotor against the inside of the housing, heads at opposite ends of the housing, and bearings for the rotor shaft, one'on each head, of an oil reservoir below the bearings and above the bottom of the inside of the rotor, there being an oil inlet to the bearing and to the rotor and an opening between the reservoir and the rotor.

5. In a vacuum pump of the sliding vane type, the combination with a body, a rotor, vanes having appreciable clearances, a hollow axle and a pulley running thereon, of oil reservoirs open to the atmosphere adapted to catch drips from the bearings and the pulley hub and to maintain a sealing body Y of oil within the rotor.

In testimony of which invention, I have hereunto set my hand, at Poughkeepsie, on this 29 day of J any., 1920.

MEREDITH LEITCH. 

